- Title
- Phylogenetic diversity and spatial and temporal variability in the bacterial populations of domestic rainwater harvesting systems
- Creator
- Evans, Craig Andrew
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2010
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Rainfall landing on the rooftops of major urban centres is a potentially valuable, but largely unexploited resource. Research indicates that widespread rainwater harvesting may provide a relatively cost competitive, energy efficient and environmentally sustainable contribution to the stabilisation of urban water supply. Current utilisation of rainwater tanks is nonetheless limited by uncertainty over quality, in relation to which a poor understanding of the general microbiology of harvested rainwater is a key factor. Predicated on a hypothetical view of the storage tank as an aquatic system, this thesis explores the possibility that rainwater tanks host diverse microbial communities, the activity of which may contribute to the incidental treatment of the water during storage. Via series of studies it provides a detailed examination of bacterial presence in harvested rainwater, addressing the diversity and distribution of bacterial populations within rainwater tanks; the influence of climatic, site, and design variables on the composition of tank communities; the general quality of tank water; and the impact of water heaters on the bacterial content of tank water. The first of these studies involved the analysis of data obtained from roof run-off samples collected throughout a series of rainfall events at a single site. Variations in bacterial counts were examined in relation to rainfall frequency, climatic conditions between events, and the meteorological characteristics of individual storms. Coliform bacteria were found to represent <0.3% of total bacterial abundance on average, and did not appear to vary in association with HPC. By comparison a significant inter-storm correlation was observed between Pseudomonas and HPC. HPC was also found correlate significantly with wind velocities, while Pseudomonas counts varied in relation to wind direction, suggesting that the majority of organisms present were likely to have been deposited by wind. The remaining studies were based on over 100 samples collected from cold and hot water tap outlets supplied by RWTs at more than twenty different locations. Examination of phylogenetic diversity within these samples revealed recovery of approximately 200 bacterial species, representing 38 different families from four major phyla. The broad composition of Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, resembled that observed in other aquatic systems, while the distribution of abundances among the taxa present approximated a log-normal pattern, characteristic of that observed in most natural microbial communities. The findings were therefore consistent with the hypothesis that rainwater tanks host diverse and potentially functional 'resident' bacterial communities. Spatial and temporal variability in the composition of these populations was examined in relation to location, vegetation over the roof catchment, roofing material, first flush diversion, tank design, seasonal, and short term temporal variation. Variation in the occurrences of several prominent genera was observed in association with factors such as regional location, roof type and leaf diverters. Tank material was associated with significant variation in bacterial abundance, possibly reflecting the influence of the tank environment on microbial activity. For all major taxa abundance was lowest and varied little among winter samples, while substantial fluctuation was evident in other seasonal groupings, indicating that the structure of resident communities may alter throughout the year. Analyses based on the period without rainfall prior to sample collection, suggested that shifts in the structure of resident communities may occur between rain events. Standard faecal indicator analysis revealed detection of E. coli in 36% of cold water samples, with counts generally below the guideline threshold for recreational waters. Comparisons of cold and hot water samples indicated lower bacterial abundance and a fundamental shift in the composition of species present in the hot water samples, which were virtually free of coliform and other Enterobacteriaceae. The tanks of this study therefore appeared to deliver hot water suitable for drinking and cooking purposes, and cold water suitable for other non-drinking household applications. In general the findings provided strong prima-facie evidence to support the putative existence of functional microbial communities within rainwater tanks, the activity of which may improve the physical, chemical, and hygienic water quality. Greater understanding of tank ecology should prove valuable in helping to, predict changes in water quality over time, identify genuine health risk, guide maintenance practices, and further optimise system design.
- Subject
- bacterial diversity; rainwater harvesting; urban centres; roof run-off; microbial communities
- Identifier
- http://hdl.handle.net/1959.13/1418349
- Identifier
- uon:37336
- Rights
- Copyright 2010 Craig Andrew Evans
- Language
- eng
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 166 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 21 MB | Adobe Acrobat PDF | View Details Download |